```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

Using `Optional[str]` instead of just `str` will let the editor help you detect errors where you could be assuming that a value is always a `str`, when it could actually be `None` too.

`Optional[Something]` is actually a shortcut for `Union[Something, None]`, they are equivalent.

    }

    /**
     * {@return the project artifacts as immutable list}. Elements are the project POM artifact and the artifact
     * produced by this project build, if applicable. Hence, the returned list may have one or two elements
     * (never less than 1, never more than 2), depending on project packaging.
     * <p>

	if errCode != ErrNone {
		t.Fatalf("Expected the APIErrorCode to be %d, but got %d", ErrNone, errCode)
	}

	inputQuery := r.URL.Query()
	// case where some headers need to get from request query
	signedHeaders = append(signedHeaders, "x-amz-server-side-encryption")
	// expect to fail with `ErrUnsignedHeaders` because couldn't find some header

   * find it when available. When this is null, use the slow way.
   */
  @J2ktIncompatible @GwtIncompatible // java.lang.reflect
  private static final @Nullable Method getStackTraceElementMethod =
      (jla == null) ? null : getGetMethod();

  /**
   * The "getStackTraceDepth" method, only available on some JDKs so we use reflection to find it
   * when available. When this is null, use the slow way.

	GO_VERSION="1.16"
	OSX_VERSION="10.8"
	KNAME=$(uname -s)
	ARCH=$(uname -m)
	case "${KNAME}" in
	SunOS)
		ARCH=$(isainfo -k)
		;;
	esac
}

## FIXME:
## In OSX, 'readlink -f' option does not exist, hence
## we have our own readlink -f behavior here.
## Once OSX has the option, below function is good enough.
##
## readlink() {
##     return /bin/readlink -f "$1"
## }
##
readlink() {
	TARGET_FILE=$1

 * </ul>
 *
 * <p>Components can be registered in two ways:
 * <ul>
 *   <li>As singletons, where one instance is shared throughout the container's lifecycle</li>
 *   <li>As prototypes, where a new instance is created each time the component is requested</li>
 * </ul>
 *
 * <p>The container supports component initialization and destruction through consumer functions,

## Do not Separate Schemas { #do-not-separate-schemas }

Now, there are some cases where you might want to have the **same schema for input and output**.

     Distributed under this Agreement, and

  b) in the case of each subsequent Contributor:
     i) changes to the Program, and
     ii) additions to the Program;
  where such changes and/or additions to the Program originate from
  and are Distributed by that particular Contributor. A Contribution
  "originates" from a Contributor if it was added to the Program by

            hash = hash * 31 + 2;
        }
        return hash;
    }

    /**
     * Sets the map of regular expressions to be used for matching.
     *
     * @param regexMap a map where the key is the field name and the value is the Pattern object
     */
    public void setRegexMap(final Map<String, Pattern> regexMap) {
        this.regexMap = regexMap;
    }

		// I/O.
		if z.IsSuspended(index) || z.IsPoolRebalancing(index) {
			continue
		}
		pool := z.serverPools[index]
		nSets[index] = pool.setCount
		g.Go(func() error {
			// Get the set where it would be placed.
			storageInfos[index] = getDiskInfos(ctx, pool.getHashedSet(object).getDisks()...)
			return nil
		}, index)
	}

	// Wait for the go routines.
	g.Wait()